From German Published Patent Application No. 196 26 576, a fuel injector is already known where an electromagnetic coil cooperates with an armature, which is in force-locking connection to a valve needle at whose spray-discharge end a valve-closure member is positioned. The armature is embodied as a plunger armature which is guided in a magnetic restrictor of the magnetic circuit. The armature is provided with a circumferential flange, which forms the upper bearing position. The guide flange is supported in the magnetic restrictor between the two poles of the magnetic circuit. As a result of this design, the guide flange of the armature and the section of the housing on which the guide flange extends, are at comparable magnetic potentials, so that no crossover of the magnetic flux occurs at the guide flange. By the guide flange being supported in the magnetic restrictor, the guide flange thus remains free of magnetic radial forces.
A particular disadvantage of the aforementioned printed publication is the large overall length of the armature, which makes a weight optimization of the armature more difficult. In addition, the circumferential guide flange on the armature obstructs the draining of fuel from the working gap, so that larger hydraulic losses result.
Furthermore, it is known to guide the section of the valve needle facing the armature inside a component of the housing. The armature is not guided in the housing or in the pole component.
Disadvantageous in the guidance of the valve needle in a guide component positioned downstream from the armature, in particular, are the radial forces which, due to an eccentric positioning of the armature, act on the component made up of armature and valve needle. Especially because of the disadvantageous lever ratios between the valve-needle guide sections and the point where the magnetic radial forces become active, this sometimes produces considerable frictional forces in the guide sections. Even slight offsets or manufacturing tolerances of the valve needle, the guide sections or the armature cause eccentric offsets of the armature, resulting in high frictional forces and, thus, in wear of the components and malfunctions of the fuel injector.